Russia and China are racing to advance their space-based military capabilities and could soon prevent the United States and its allies from using outer space freely.

The warning, in a new report Monday from the Defense Intelligence Agency, builds on a series of warnings issued by the defense and intelligence communities over the past several years.

But unlike many previous assessments, which focused on Russian and Chinese efforts to match or counter U.S. capabilities, the new DIA report suggests both countries are pursuing a far more aggressive agenda.

"They are developing systems that pose a threat to freedom of action in space," the report warned, citing current Russian and Chinese military doctrine that sees the ability to control outer space as "integral to winning modern wars."

U.S. defense intelligence officials believe Russia and China have spent the past four years increasingly aligning their militaries around the importance of space operations.

FILE - Visitors look at a model of China's Tiangong-1 space station at the China Beijing International High-Tech Expo in Beijing, June 10, 2017. China was excluded from the International Space Station largely due to concerns over its space program's connections to the military and U.S. legislation barring such cooperation. That didn't stop the country from launching its own space laboratory in 2011, named Tiangong ("Heavenly Palace"), which orbited Earth until last April.

Already, those efforts have resulted in what officials describe as "robust and capable" space services for both countries, with improvements constantly in the works.

Additionally, Russia and China now have "enhanced situational awareness, enabling them to monitor, track and target U.S. and allied forces," the report said.

Both countries have also made gains in tracking U.S. space assets.

"Chinese and Russian space surveillance networks are capable of searching, tracking, and characterizing satellites in all Earth orbits," the report added.

Such capabilities are critical in order for Russia and China to successfully use a variety of systems that could eliminate or incapacitate U.S. satellites, from directed energy weapons to anti-satellite missiles.

While the DIA report warns Russia and China pose the greatest threats to the U.S. in space, other countries are also taking aim at U.S. dominance in space, including Iran and North Korea.

Both Tehran and Pyongyang have shown the ability to jam space-based communications and "maintain independent space launch capabilities."

In January, the U.S. issued a new National Intelligence Strategy, which warned of growing competition in space.

The strategy, by the Office of the Director of National Intelligence, said both Russia and China are pursuing "a full range of anti-satellite weapons, which could degrade U.S. intelligence gathering abilities."

The U.S. Worldwide Threat Assessment issued late last month also said China already has an anti-satellite missile capable of hitting satellites in low-Earth orbits, while Russia has been field testing ground-based laser weapons.